The atmosphere of ____________ contains mostly nitrogen with some methane
a. Jupiter
b. Earth's Moon
c. Callisto
d. Titan
e. Miranda
d
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What number of turns on the secondary is needed to reduce the voltage from 120 V to 9.0 V if there are 40 turns on the primary of a step down transformer?
A. 3 B. 9 C. 18 D. 120 E. 530
In Ptolemy's geocentric model, retrograde motion occurs when the planet is closest to us, on the inside portion of the
A) ellipse. B) epicycle. C) equant. D) ecliptic. E) deferent.
What was the Stardust mission?
A) a mission to study the composition of an asteroid by hitting it with a massive object and observing the material thrown into space B) a mission to study the outer planets of the solar system by sending a probe from one to the next with a wide variety of instruments C) a mission to study the composition of a comet by collecting material from its tail and return that material to Earth D) a mission to study the surface structure of a comet by dropping a lander onto its surface
A solar collector design consists of several parallel tubes each enclosed concentrically in an outer tube that is transparent to solar radiation. The tubes are thin walled with the inner and outer cylinder diameters of of 0.10 and 0.15 m respectively. The annular space between the tubes is filled with air at atmospheric pressure. Under operating condition the inner and outer tube surface temperatures are 70°C and 30°C respectively.
(a) What is the convective heat loss per meter of tube length?
(b) If the emissivity of the outer surface of the inner tube is 0.2 and the outer cylinder
behaves as though it were a black body, estimate the radiation loss.
(c) Discuss design options for reducing the total heat loss.
GIVEN
? Thin walled concentric tubes with air atmospheric pressure between them
? Inner tube diameter (Di) = 0.1 m
? Outer tube diameter (Do) = 0.15 m
? Inner tube temperature (Ti) = 70°C = 343 K
? Outer tube temperature (To) = 30°C = 303 K
? Outer surface emissivity of inner tube (E) = 0.2
FIND
(a) The convective loss pe meter of tube (qc/L)
(b) The radiative loss (qr/L)
(c) Discuss design options for reducing the total heat loss
ASSUMPTIONS
? Steady state
? Tubes are horizontal
SKETCH
PROPERTIES AND CONSTANTS
